The proposed research has the long-term goal of increasing the sensitivity and range of application of clinical chemiluminenscent immunoassays. Substantial public benefits could follow. Specific objectives: (1) Prepare preliminary assay substrates by plasma surface modification. (2) Test substrates for background luminescence and non-specific protein binding. (3) Prepare additional substrates using designated plasma monomers. (4) Test substrates for background luminescence and chemiluminescence levels in immunoassays. (5) Analyze results and describe their relevance to a Phase II program leading to expanded commercial applications of chemiluminescent assay.